The invention relates to an apparatus for ascertaining the impermeability to gases of connections between pieces of piping, especially between pipes and sleeves, by utilizing two ring-shaped elastic sealing bodies which are spaced apart from one another and whose diameters are variable in response to axial stressing by pressure applying pistons which are movable in the longitudinal direction of the piping. The location to be tested is disposed between the seals and is confined by a sealing flange which is provided with a bore for evacuation of leak gas to measuring instruments.
In order to eliminate leaks in connection between pipes, it is customary to subject the pipings to a test for the determination of leaks before the pipings are put to use, for example, prior to being lowered into a borehole. To this end, a pressurized testing medium is applied to the connection and the pressure is monitored to ascertain a drop of pressure.
In accordance with a further testing procedure for determination of leaks, it is known to convey a gas through two pieces of piping which are connected to each other. The gas pressure is applied from within with assistance from a sealing tool. Such method and a tool for the practice of the method are disclosed, for example, in German Offenlegungsschrift No. 30 30 665. This publication shows two ring-shaped seals of resiliently yieldable material which are spaced apart form each other and are biased axially against each other by two pistons each of which cooperates with one of the seals. In this manner, one ensures that the seals abut the internal surfaces of the pieces of piping which are connected to each other to form a testing chamber into which the testing gas, for example helium, is admitted at elevated pressure. In the region of testing locations, the other side of this testing chamber is connected with measuring instruments which detect ("sniff") the quantities of gases that happen to escape. However, the tool is not suitable for the testing of sealing locations between short pieces of piping, especially not in the case of connection of the end of a pipe to a sleeve, because the testing location is disposed at a short distance from the free end of the sleeve or from the end of the pipe. The conventional tool is suitable only for insertion, in its entirety, into pipes which are connected to each other and is thus suitable for use in a drilling tower.